<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html{
            height: 100%;
        }
        body{
            height: 100%;
        }
        .box{
            background-color: pink;
        width: 50%;
        height: 50%;
        
        }
        
    </style>
</head>
<body>
    <div class="box">盒子</div>

</body>
</html>